Field of invention
[0001] The present invention relates to a system and a method for providing the design of
a dental post and core, in particular relating to CAD/CAM design/manufacture of post
and core. A post and core is typically a part of a dental restoration. Moreover, the
invention relates to a computer-readable medium for implementing such a system on
a computer.
Background of invention
[0002] A post and core is a dental restoration used to sufficiently build-up tooth structure
for future restoration with a crown when there is not enough tooth structure to properly
retain the crown due to loss of tooth structure to either decay or fracture. In many
cases the dental root is removed leaving an empty root canal in the tooth. Typically
a thin rigid post (e.g. metal post) is inserted into the root canal and this post
provides retention for a "core" which is a build up of material that replaces the
lost tooth structure. The post can be cemented within the root canal and the core,
which is an artificial preparation provides retention for the crown or coping replacing
the tooth. The term "post and core" is also referred to as "post-and-core" and "inlay
core". Post and core restorations are often characterised as "foundation restorations".
[0003] In a root canal procedure the nerve of the tooth is typically removed by the dentist
using a dental drill, a so called endodontic procedure, leaving a bore in the tooth.
In many cases a special post can be provided that matches the shape of the drill and
after drilling the post can be directly cemented in the bore. However, the tooth root
canal may have a non-regular structure and the bore in the tooth after removing the
root is often also irregular, but even for the regular shapes the depth of the bore
may be unknown. No post can thereby match the bore and a custom post must be provided.
[0004] A typical procedure when designing a post and core is that the dentist provides an
impression of the prepared tooth with the bore and possibly also adjacent teeth and
sends it typically to a dental technician at a dental laboratory. From this impression
a dental model, such as a gypsum model, can be poured, and the dental restoration
including the post and core can now be build from the dental model. The dental technician
typically builds the post and core in wax, and then performs an investment casting,
such that the real post and core is manufactured in a suitable material, e.g. a metal
alloy.
[0005] The article "
Fabrication of a custom-made ceramic post and core using CAD-CAM technology" by Awad
et al. from J. Prosthet Dent 2007; 98; 161-162 discloses the use of CAD-CAM technology to fabricate a custom-made ceramic post and
core, which includes the fabrication of a direct acrylic resin pattern, i.e. wax,
to capture the anatomy of the canal, and then the pattern is scanned, milled and sintered.
The pattern is fabricated by the manual method of lubricating the canal with either
water or saliva, then placing autopolymerizing acrylic resin on the plastic core with
a brush and placing the post into the canal. The post is maintained in position for
a few seconds, and then quickly removed for determining if the entire anatomy of the
canal was recorded. If needed, more acrylic resin is applied to the post, the post
is placed back into canal before it completely polymerizes, and then moving the post
in and out of the canal until it is passively inserted and removed. Then the post
pattern is placed into the canal and the core is added. The post and core pattern
is attached to the scanning ring of the CAD system, and then scanning and milling
of the patterns is performed. Thus according to the disclosure the scanner of the
CAD system is used to scan the shape of a custom-made plastic sample post and core
for manufacturing the real ceramic post and core on a milling machine, so called copy
milling.
[0007] Thus it remains a problem to provide a more efficient and high quality CAD-CAM procedure
for providing post and cores.
Summary of the invention
[0008] Disclosed is a computer-implemented method of designing and/or manufacturing a post
and core to match a bore of a tooth, said method comprising the steps of:
- a) obtaining at least one impression of a set of teeth comprising a bore;
- b) scanning the impression of the set of teeth comprising the bore;
- c) providing a three-dimensional scan representation of the impression comprising
the bore;
- d) transforming the three-dimensional scan representation to a three-dimensional positive
working model of the set of teeth and the bore; and
- e) designing a post and core model from the positive working model of the bore.
[0009] WO 2007/062658 discloses a computer implemented method for obtaining orientation and localization
of a dental implant comprising the step of scanning the impression of the bore in
the jaw bone.
[0010] FR1456600 discloses a system for manufacturing a dental post by using the impression of the
root canal.
[0011] Thus it is an advantage that the method provides a way of resolving the structure
of a tooth bore to provide a matching post and core. Thus the method solves the problem
that during conventional 3D scanning of a dental gypsum model with a bore it is virtually
impossible for the scanner to resolve the structure of the narrow tooth cavity, i.e.
the bore, as seen in fig. 11. Thus traditionally it is not possible to examine the
structure or shape of the bore in the prepared tooth. This is because 3D scanners
for scanning, e.g. dental models, uses the well-known triangulation principle to obtain
the 3D scan, and if the bore is too narrow or has a non-regular shape, the sensors
of the scanner, e.g. camera or light projector, cannot measure all points in the bore.
[0012] Impression scanning is known in the art. However, this invention relates to scanning
of the impression of a bore. A tooth impression will provide a negative representation
of the tooth, i.e. the tooth will be a hole in the impression, however an impression
of a bore / cavity will be a spike in the impression. Thus when scanning an impression
of a bore, a good result of the scanning can be obtained, because there will no areas
of the bore that the scanner cannot gain access to, because the bore in the impression
is formed like a spike and not like a narrow cavity as in a positive model.. Thus
an impression of the bore becomes the basis of the post and core model, in particular
in designing a post matching the bore.
However, in order to get a good representation of the unmodified teeth, the impression
scan can be inverted or transformed to a positive model, where the teeth have an extent
or expand instead of being holes. In this virtual positive model, the bore is a narrow
cavity.
The virtual 3D model which is transformed or inverted from the impression scan representation
may be denoted a virtual working model, because the post and core can be formed using
the virtual working model. The virtual working model may be modified, adjusted, formed
and shaped such that it resembles a physical model, e.g. resembling a gypsum model,
so that the visual appearance of the virtual working model makes it easy for a dental
technician to perform the designing, if he/she is used to working with a physical
model.
The post and core can be designed using the virtual working model, such that it is
easy for the dental technician to visualize how the real post and core will look and
fit into the mouth of a patient.
[0013] Transforming or inverting the scan representation of the impression to the positive
working model can be performed by rotating the representation, inverting the points
of the representation, and/or performed in other ways known to the skilled person
etc.
The positive working model may be created by e.g. deleting some of the sides, if they
for instance provide shade or shadow for some of the teeth in the model, a base may
be created for the positive virtual working model, and the post and core in the virtual
working model may be marked and provided as a section which can be virtually removed
or taken out from the model.
[0014] Traditionally, due to problems of generating a correct virtual 3D model from scanning
a teeth impression, impression scanning is often only a supplement to the gypsum dental
model. However, when designing a post and core according to the present invention,
casting the dental model in e.g. gypsum may be omitted thereby providing a more efficient
and high quality CAD/CAM procedure and reducing the risk of error.
[0015] It is an advantage that CAD/CAM technology for designing and manufacturing dental
restorations result in improved quality, reduced cost and facilitation of the possibility
to manufacture in attractive materials otherwise not available, e.g. zircon.
[0016] It is an advantage that CAD/CAM technology provides high accuracy, since accuracy
requirements for dental restorations are very high otherwise the dental restoration
will not be visual appealing, fit onto the teeth, could cause pain or cause infections.
[0017] Thus CAD/CAM technology can be used for designing and manufacturing dental restorations.
The first step in a conventional or traditional CAD manufacturing process is to create
a 3-dimensional dental model of the patient's teeth. This can conventionally be provided
by 3D scanning a dental gypsum model. The 3-dimensional replicas of the teeth are
imported into a CAD program, where the entire dental restoration or a substructure
is designed. The final restoration 3D design is then manufactured e.g. using a milling
machine, 3D printer, rapid prototyping manufacturing or other manufacturing equipment.
[0018] It is thus an advantage of the present method that the dental gypsum model might
not need to be manufactured, because the post and core can be designed completely
digitally without using any manually prepared physical model. The dental technician
needs therefore not to pour the gypsum model, and this saves time and material, so
the turn-around time is reduced, which is an advantage.
Some dental technicians may however still wish to have a physical working model, on
which they can test and adjust a post and core model. It is therefore an advantage
that the post and core model can be manufactured according to the present method,
and simultaneously a physical working model can be manufactured also using CAD/CAM.
Thus the turn-around time is still reduced, because the post and core model and the
physical working model can be manufactured simultaneously, and the designing or manufacturing
of one of them is not dependent on the designing and manufacture of the other one.
[0019] Manufacturing according to the present method may be performed using CAM technologies,
such as:
- milling;
- 3D printing;
- 3D laser sintering;
- moulding.
[0020] Materials to be used in the manufacturing may be:
- zircon oxide;
- ceramics;
- wax;
- precious alloys;
- non-precious alloys.
[0021] According to an aspect of the invention a method for designing and/or manufacturing
a post and core to match a bore of a tooth is disclosed, said method comprising the
steps of:
- scanning at least one impression of the bore, preferably a jaw dental impression comprising
an impression of the bore; thereby
- obtaining a three dimensional model of the impression, said three dimensional model
comprising a positive model of the bore, and
- creating a post and core model from the positive model of the bore.
[0022] In an embodiment the step of obtaining a three-dimensional model of the impression
comprises providing a three-dimensional scan representation of the impression, and
transforming the three-dimensional scan representation of the impression to the virtual
three-dimensional model comprising the bore.
[0023] In some embodiments the virtual three-dimensional working model is configured to
be trimmed, and/or provided with a base, and/or articulation tested, and/or provided
with sectioned preparations preserving the gingival. In some embodiments manufacturing
comprises manufacturing the post and core design and/or manufacturing the working
model.
[0024] In some embodiments the step of scanning at least one impression comprises:
f) performing an initial scan of the impression;
g) creating a visibility function based on a virtual model of the scanner performing
the scanning and the initial scan of the impression, said visibility function being
capable of evaluating the coverage of areas of interest of the impression by at least
one predetermined scan sequence;
h) establishing at least one scan sequence based on the evaluation of the visibility
function;
i) performing a scan of the impression using said at least one scan sequence;
j) optionally repeating steps h) and i) at least once until the three dimensional
model of the impression is obtained.
[0025] The above embodiment may be called adaptive scanning, because the scanning is adapted
to the specific object, or in this case, impression. Adaptive scanning is an advantage
because it enables that full geometrical coverage of the impression is obtained. A
problem with 3D scanning, using e.g. structured light, is that both the camera and
light pattern of the scanner need to "see" each surface point at the same time to
be able to make a 3D reconstruction of that particular point. If this is not fulfilled,
this leads to "occluded" or uncovered areas which appear as surface holes in the final
scan, i.e. areas without surface measurement information. Holes in the scan are in
most cases undesirable or unacceptable both from a visual and application point of
view. However, when using adaptive scanning the initially uncovered areas will also
be covered, because the scanner software registers where the uncovered areas are on
the impression and then performs scanning sequences directed to these specific areas.
[0026] In a further object of the invention a model for the post may be provided independently
and/or separately and/or in a separate step from creating a model of the core. I.e.
the post must match the bore and the core must match the post and the adjacent teeth,
and vice versa: the post must match the core matching the adjacent teeth. Creating
models of post and core in separate steps further requires a step of merging / combining
the models.
[0027] The term "post and core" comprises the post being inserted in the bore and the core
attached to the post becoming retention for a dental restoration. The post and core
can be designed and/or cast and/or designed and/or manufactured in one piece or in
two or more pieces. Thus, the "post and core model" is a 3D model of a "post and core".
[0028] The term "post" refers to the part of a post and core being inserted in the bore.
Thus, a "post model" is a 3D model of the post only.
[0029] The term "core" refers to the part of a post and core that is retention of a dental
restoration. Thus, a "core model" is a 3D model of the core only.
[0030] The term "bore" refers to a drilled cavity / bore in a prepared tooth. A "bore model"
is a 3D model of the bore.
[0031] The term dental impression may also be denoted jaw impression.
[0032] When removing the tooth root / tooth nerve the dentist have used one or more dental
drills. Thus, the shape of the resulting tooth bore is at least partly determined
by the shape and/or type of the drill(s) processing the bore. In a further embodiment
of the invention the post and core model and/or the post model is matched with the
shape of the dental drill that created the bore. This is provided to improve the post
and core model. Matching the shape can be merging and/or combining shape information
of the dental drill(s) that created the bore, shape information such as a CAD model
of the drill(s). Thereby scan artefacts of the post and core model can be identified
and/or removed. E.g. a notch or cut in the post and core model can be identified as
a scan artefact by knowing that use of the particular drill used could not have provided
such a notch or cut.
[0033] When a post and core, or a dental restoration comprising the post and core, is mounted
in the mouth of a patient the insertion direction is not necessarily coinciding with
the direction of the main axis of the post. Especially the adjacent teeth necessitate
that care must be taken when designing the post and core model. The direction and
structure of the tooth bore is often mainly determined by the root canal. Thus, in
a further embodiment of the invention the insertion direction of the post and core
is determined. This can e.g. be provided by taking into account the direction of the
bore, the main axis of the bore, position and inclination of the lost tooth / teeth
and adjacent teeth, structure of root canal, position and inclination of coping, and/or
crown, position in the jaw and/or the like.
[0034] When processing the tooth during drilling or root canal therapy, the resulting bore
may be highly irregular, in some cases because removal of the entire tooth root results
in an irregular shape. Thus, in some cases a post and core model with a post exactly
mirroring the bore is impossible to insert in the bore, e.g. due to undercuts in the
bore. Another issue is when a determined insertion direction makes it impossible to
insert the post and core into the bore. Therefore a further embodiment of the invention
relates to performing undercut removal of the post and core model to allow for insertion
of the post and core into the bore.
[0035] In a further embodiment of the invention the post and core model can be reduced,
reshaped, optimised and/or changed to allow for a cement space or cement gap, such
as a cement layer, when attaching or fixing the post and core in the bore. This can
be provided manually, automatically and/or semi-automatically. E.g. a layer of certain
predefined thickness which can be accounted for, e.g. by reducing the post and core
model. The cement space may also have varying thickness depending on the structure
of the bore. When accounting for the cement space, issues relating to the insertion
direction and undercut removal may be relevant. E.g. the cement space is depending
on the undercut area(s). The total volume of the cement space may also be calculated,
possibly based on undercut removal, insertion direction, drill shape, scan artefacts,
bore structure and the like. The total volume of the cement space may provide an indication
of the necessary amount of binding material, such as cement, to use when mounting
the final post and core in the bore.
[0036] A post and core typically comprises at least one rigid post to increase the strength.
A rigid post such as a metal pin or metal post. Thus, a post and core may be custom
designed around a standard (rigid) post. The rigid post may be present in the impression
of the bore. I.e. the impression is provided with one or more rigid posts surrounded
by impression material. The rigid post(s) in the impression may be the real post(s)
used in the final post and core or may be a duplicate model of a rigid post. When
scanning the impression the rigid post will become a part of the post and core model
and/or the post model. Thus a post model may comprise a rigid post. In a further embodiment
of the invention the post and core model is improved and/or optimised by integrating
and/or merging shape information of the rigid post with the post and core model and/or
the bore model and/or post model. Shape information in terms of e.g. a CAD model of
the rigid post.
[0037] In a further embodiment of the invention the rigid post (i.e. the model of the rigid
post) is identified, separated, removed, deleted and/or extinguished from the post
and core model and/or the post model. This can be provided when having shape information
of the post, i.e. the post can be "recognised" in the 3D post and core model. When
knowing the shape of the post and when the post is identified in the 3D model, the
post can also be taken out of the post and core model and/or the post model. Possibly
leaving a hole / cavity / void in the post and core model and/ the post model. Thereby
a post and core model without post can be provided. Thereby the final post and core
can be manufactured without the post, and the post may subsequently be inserted in
the final post and core.
[0038] When taking the impression of the tooth and bore the dentist may use a longer post
than the depth of the bore to facilitate control of the impression process, e.g. the
post can be provided with a handle. After obtaining an impression scan this handle
can be part of the post and core model. In a further embodiment of the invention the
post is cut in the post and core model, preferably cut in a length relating to e.g.
the dental restoration, the gingiva and/or the margin line.
[0039] In some embodiments the post and core margin line(s) are configured to be automatically
arranged based on a margin area.
Thus the margin line for the post and core can be determined automatically or manually
at the position where the post and core ends, e.g. in the end of the post and core,
when arranged in the positive model.
[0040] In some embodiments the shape of the core and/or the coping and/or the crown are
configured to be selected from a number of different predefined shapes.
An advantage of this embodiment is that the dental technician or user can select e.g.
a core with the shape he wishes, or with a shape which suits the specific case. Hereby
account can be taken of material requirements, thickness of the different layers of
the restoration, etc.. Using an anatomical reduction, the shape of the post and core
can also be derived from the crown or coping shapes if these are designed prior to
the post and core.
[0041] In some embodiments the shape of the core and/or the coping and/or the crown are
configured to be changed by a digital sculpt-tool.
An advantage of this embodiment is that the dental technician can use the sculpt-tool
to obtain design flexibility. The sculpt-tool may provide both a freeform and an automatic
tool, e.g. a virtual wax knife, freeform morphing of any part of a surface, transformations
for global repositioning, automatic smoothing, automatic minimum material enforcement
and automatic high aesthetic cut to antagonist or gingival.
[0042] Some teeth may provide multiple root structure with multiple "main axes", i.e. root
canals in multiple non-parallel directions. This is especially the case with the molar
and premolar teeth. Thus, in a further embodiment of the invention the post and core
is a split core, such as a split core for a multiple root tooth. This may provide
a more advanced post and core model, e.g. comprising multiple non-parallel posts to
strengthen the post and core.
[0043] Instead of inserting multiple posts in the bore of a multiple root structure a single
post may provide enough strength for the post and core. The post and core is then
designed around the single post, however the multiple root structure may need multiple
post and core structure to fill the entire cavity of the multiple roots. In a further
embodiment of the invention the bore is at least partly filled prior to inserting
the post and core, preferably to simplify the necessary shape and structure of the
post and core. This may for example be provided prior to obtaining an impression of
the bore. Alternatively filling may be provided after obtaining an impression of the
bore.
In some embodiments the method further comprises virtual filling of one of the bores
when designing the post and core for a case with multiple bores, and then designing
the post for the remaining bore(s).
[0044] In a further embodiment of the invention the post and core model and/or the dental
restoration model is combined with or supplied with other imaging techniques, such
as X-ray scans, CT scans, intraoral scans etc.. X-ray image(s) of the prepared tooth
and/or adjacent teeth may provide additional information of the bore and the prepared
tooth, i.e. structure, volume, directions and/or the like. This can for example assist
in identifying scan artefacts. X-ray imaging may also provide information of the general
condition of the tooth, i.e. any hidden fractures of thickness of remaining bone structure.
Typical features that are not obtained from the impression. Knowing the general condition
of the tooth may also provide information of how much pressure can be applied to the
prepared tooth and/or adjacent teeth, thereby for example being able to determine
the length, shape, structure and/or thickness of the post to be applied and/or whether
tooth enforcement, such as a tooth band, is necessary.
[0045] When designing the post and core model a correct fit to the bore is crucial. Thus,
in a further embodiment of the invention, the bore model and the matching post and
core model and/or post model can be visualised, preferably visualised concurrently.
Preferably the match between the post and core model and/or the post model and the
bore model can be visualised, such as visualised like plug-and-socket.
[0046] In some embodiments the method further comprises any of the steps of:
- providing an interface between the post and core model and the dental restoration
model
- inverting the three dimensional impression model and/or merging the post and core
model with a dental model comprising the prepared tooth, thereby obtaining a dental
model comprising the prepared tooth and the bore,
- adding a base for the dental restoration model,
- determining the insertion direction of the dental restoration,
- removing scan artefacts, and/or
- adding at least one coping or crown to the model.
[0047] In another embodiment of the invention designing and/or manufacturing at least a
part of a dental restoration comprising a post and core is provided. A post and core
is typically part of a dental restoration. Thus, further steps are preferably provided
to design the dental restoration around or on top of the post and core. The post and
core model is provided by means of the positive model of the bore. However, the impression
comprising the bore typically comprises a negative representation of the prepared
tooth and the adjacent teeth. A positive dental model of these can e.g. be provided
by inverting the three dimensional impression representation. A dental model can also
be provided by scanning a cast model of the teeth and subsequently merging and/or
combining the post and core model with the dental model. However, preferably both
the post and core model and the dental model are provided from an impression scan.
And preferably they are combined and visualised in a double sided rotatable 3D model
as shown in figs. 3A and 3B, showing both the negative representation and positive
model of post and core and teeth. Thus the virtual positive working model can be created
from the scan representation of the impression.
[0048] A base may further be added to the dental restoration model. Preferably the insertion
direction of the dental restoration is determined automatically or semi-automatically
but may preferably also be adjusted manually by a user. In a further embodiment of
the invention the dental restoration is a bridge.
[0049] In some embodiments the at least one coping or crown is automatically positioned
on the post and core.
[0050] In some embodiments the position of the coping or crown is configured to be adjusted.
[0051] In some embodiments the crown and/or coping is designed before designing the post
and core.
Thus either the crown and/or coping is designed first, and then the post and core
is designed after this, such that the crown and/or coping determines the shape of
the post and core, in particular determines the shape of the core, which the crown
and/or coping is attached to.
Otherwise the post and core is designed first, and then the crown and coping is designed
after this, such that the post and core determines the shape of the crown and/or coping.
[0052] In some embodiments the shape of the post and core is configured to be derived from
the shape of the crown and/or the coping.
[0053] After root canal therapy a tooth may be severely reduced in strength. And mounting
a post and core in the tooth vertical forces applied to the post and core (e.g. by
chewing or jaw clenching) may be transferred to horizontal forces in the tooth root
possibly leading to fracture in the root. This can be prevented by means of a tooth
band applied around the tooth near the margin line and/or gingiva. This can be accounted
for by applying, designing, integrating or merging a tooth band or a model of a tooth
band to the dental restoration model. A tooth may be applied to the prepared tooth
prior to the impression, and the tooth band or a negative representation of it, will
therefore appear in the three dimensional model obtained from the impression. Preferably
the dental model can be improved by combining and/or merging with shape information
of tooth band, e.g. CAD models of tooth bands.
[0054] In some embodiments the post and core design automatically is retrieved from an electronic
library, so that the post and core has a correct anatomical fit relative to the bore.
[0055] In some embodiments a cement gap in the bore is defined so that there is space for
adding cement or glue into the physical bore before the post and core is fixed.
In a further embodiment of the invention combining, integrating and/or merging of
impression scans obtained from multiple and/or different impressions are provided.
This can for example be provided to improve the post and core model and/or the dental
restoration model and/or the dental model. E.g. selected parts of a model can be rescanned,
possibly in greater detail, and then merged into the original model. Single sided
and/or double sided impressions and/or lower jaw dental impression and/or upper jaw
dental impressions may be scanned, provided, and/or combined.
[0056] In some embodiments at least one of the steps are provided by means of CAD/CAM.
[0057] The present invention relates to different aspects including the method described
above and in the following, and corresponding methods, devices, system and/or product
means, each yielding one or more of the benefits and advantages described in connection
with the first mentioned aspect, and each having one or more embodiments corresponding
to the embodiments described in connection with the first mentioned aspect and/or
disclosed in the appended claims.
[0058] In particular, the invention furthermore relates to a system comprising means for
providing any of the listed methods. The invention furthermore relates to a computer
program product comprising a computer readable medium, said computer program product
comprising means for carrying out all the steps the listed methods.
Brief description of the drawings
[0059] The above and/or additional objects, features and advantages of the present invention,
will be further elucidated by the following illustrative and nonlimiting detailed
description of embodiments of the present invention, with reference to the appended
drawings, wherein:
Fig. 1 shows a picture of a dental impression.
Fig. 2 schematically illustrates a dental restoration comprising a post and core.
Fig. 3 shows a 3D model which is the result of an impression scan.
Fig. 4 schematically illustrates a post and core with two pins.
Fig. 5 schematically illustrates a dental bridge comprising a post and core.
Fig. 6 is a blow up of the post model in fig. 3.
Fig. 7 is an example of a flow-chart showing the method.
Fig. 8 shows the entire work flow of the method.
Fig. 9 shows an example of a virtual working model.
Fig. 10 shows examples of different steps which can be used when designing a post
and core.
Fig. 11 shows an example of undercut areas in a preparation.
Detailed description
[0060] In the following description, reference is made to the accompanying figures, which
show by way of illustration how the invention may be practiced.
[0061] Fig. 1a) is a picture of a dental impression comprising a standard rigid post for
a post and core. The rigid post is shown in greater detail in the blow up.
Fig. 1b) is a picture of another dental impression comprising an impression of a bore.
The impression of the bore is here made in a different material than the rest of the
impression. The impression of the bore is irregular.
Fig. 2 illustrates schematically a dental restoration comprising a post and core 21.
The post and core 21 comprises the post 26 entering and matching the bore of the tooth
24 and the core 27 that provided retention of the coping 22 and the crown 23. The
damaged tooth 24 has been prepared, i.e. it has been grinded down close to the gingiva
25 and a bore has been provided by means of a dental drill. The post and core 21 matches
the bore of the prepared tooth 24. The post and core 21 also provides retention /
support for the coping 22 and the crown 23. The post and core 21, the coping 22 and
the crown 23 can all be designed / provided according to the present invention.
[0062] Figs. 3A and 3B show a three dimensional model which is the result of an impression
scan. Fig. 3A is the 3D scan representation of the impression showing the teeth in
negative representation and with an impression 32 of the bore 31 forming a spike-like
form becoming the basis for the post and core model. A blow up of the positive impression
32 is shown in fig. 6.
Fig. 3B shows a virtual 3D positive model, e.g. working model, of the set of teeth
and tooth bore, which is an inversion or transformation of the 3D representation of
the impression in fig. 3A. A dental restoration comprising a post and core can be
designed according to the invention with basis in a 3D model as shown in fig. 3.
[0063] Fig. 4 illustrates a post and core with two posts 42, 43 and a core 41, for a tooth
with multiple bores. Due to the different directions of the bores the post and core
must be divided in at least two parts to provide insertion of both posts 42, 43 into
the bores. In one embodiment of the invention design and/or manufacture of a post
and core for a multiple bore tooth is provided. The post and core model is divided
in at least two parts, such as a part for each bore, providing insertion of the post
and core into the bore. Insertion directions for each part and/or for each bore are
preferably provided.
[0064] Fig. 5 shows a model of a dental bridge 52 with retention in a post and core 51.
The bridge 52 is provided to support the pontic 53 replacing a lost tooth. The post
and core 51 provides retention for the bridge. With the thick arrows it is illustrated
that the insertion directions of the post and core 51 and the bridge 52 are different.
The post and core 51 is designed to match the bore 55 and the insertion direction
of the post and core 51 is calculated to provide insertion of the post and core into
the bore 55. However, the upper part of the post and core 51 providing retention for
the bridge 52 is designed to be parallel with the calculated insertion direction of
the bridge 52.
[0065] Fig. 7 shows an example of a flow-chart of a method for designing and/or manufacturing
a post and core to match a bore of a tooth. In step 701 scanning of at least one impression
of the bore is performed. Preferably the impression is a dental impression comprising
an impression of the bore, whereby a three dimensional model of the impression is
obtained, where the three dimensional model comprises a positive model of the bore.
In step 702 creation of a post and core model from the positive model of the bore
is performed.
[0066] Fig. 8 shows an example of how the entire work flow can be according to the method.
In step A an impression is shown. The impression is made in a patient having a bore,
into where a post and core should be fixed. A metal working-post is provided in the
impression where the bore is, so in this case the bore forms a spike in the impression
by means of the working-post. In other examples the bore forms a spike in the impression,
where the spike is of the same material as the rest of the impression.
[0067] In step B the impression has been scanned, and the scanned image of the impression
is shown. The bore is seen as a spike.
In step C a virtual positive model of the teeth is created from the scanned representation
of the impression. The bore becomes a cavity in the positive model. Since both the
negative representation and the positive model are available as digital images, the
bore can be seen from all sides and there are no uncovered areas, whereby the post
and core for fitting into the bore can be designed to fit perfectly into the bore.
In step D a drawing of a created post and core for perfect fitting into the bore is
shown. The reference numbers on the drawing are explained in fig. 2.
[0068] Fig. 9 shows an example of a virtual working model.
The virtual working model 901 comprises non-modified teeth 902 and prepared teeth
903, which are prepared for dental restorations. One of the prepared teeth 903 or
dental restorations may be a post and core restoration. The working model in the figure
has been trimmed, i.e. the scans forming the model are trimmed, the model is provided
with a base and with sectioned preparations preserving the gingival. Furthermore,
the model can be articulation tested.
[0069] Fig. 10 shows examples of different steps which can be used when designing a post
and core.
Fig 10a) shows the post and core model 101, where the dots 102 indicate the area of
the margin line 103.
Fig. 10b) shows the post and core model 101 with an indication of the insertion direction
104 of the bore or post 105.
Fig. 10c) shows the post and core model 101 with insertions direction 104 and margin
line 103.
Fig. 10d) shows the designed post and core model 112 fitted into the full model 106,
or working model or model of the rest of the set of teeth, or dental model. A cement
space 107 is included between the designed post and core model 112 and the model 106.
Fig. 10e) shows a cross-section 108 through the model 106 and through the post and
core model 112. The image in lower right part of fig. 10e) shows this cross-section,
where the cement space 107 is also seen.
Fig. 10f) shows the model 106 and a crown 109 attached to the designed post and core.
Fig. 10g) shows the model 106 and the crown 109 and the core 110 underneath the crown,
where the crown 109 has been adjusted to fit the model 106.
Fig. 10h) shows the model 106 and the crown 109 and the core 110, where undercut removal
of the core 110 has been performed, such that the attachment of the crown 109 to the
core 110 will be unproblematic.
Fig. 10i) shows the complete post and core 112 in the model 106, where the post and
core comprises the core 110 and the post 111.
[0070] Fig. 11 shows an example of undercut areas in a preparation.
The figure shows why a scanner cannot obtain image information of undercuts or hidden
areas in a preparation. A scanner 201 comprises a light projection 202 and a camera
203 for capturing the reflected light. The scanner 201 is scanning a tooth preparation
204 with undercuts 205, but as seen the scanner cannot obtain image information at
the undercuts 205, because the light projection 202 and/or the camera 203 cannot gain
access to the points of the undercut. Thus the undercuts are uncovered areas.
[0071] Although some embodiments have been described and shown in detail, the invention
is not restricted to them, but may also be embodied in other ways within the scope
of the subject matter defined in the following claims. In particular, it is to be
understood that other embodiments may be utilised and structural and functional modifications
may be made without departing from the scope of the present invention.
[0072] In device claims enumerating several means, several of these means can be embodied
by one and the same item of hardware. The mere fact that certain measures are recited
in mutually different dependent claims or described in different embodiments does
not indicate that a combination of these measures cannot be used to advantage.
[0073] It should be emphasized that the term "comprises/comprising" when used in this specification
is taken to specify the presence of stated features, integers, steps or components
but does not preclude the presence or addition of one or more other features, integers,
steps, components or groups thereof.
[0074] The features of the method described above and in the following may be implemented
in software and carried out on a data processing system or other processing means
caused by the execution of computer-executable instructions. The instructions may
be program code means loaded in a memory, such as a RAM, from a storage medium or
from another computer via a computer network. Alternatively, the described features
may be implemented by hardwired circuitry instead of software or in combination with
software.
1. A computer-implemented method of designing and/or manufacturing a post and core (21;
41, 42, 43; 51; 110, 111) to match a bore (31) of a tooth (24), said method comprising
the steps of:
a) obtaining at least one impression of a set of teeth, said set of teeth comprises
a bore;
b) scanning the impression;
c) providing a three-dimensional scan representation of the impression;
d) transforming the three-dimensional scan representation to a virtual three-dimensional
positive working model (106) of the set of teeth and the bore; and
e) designing a virtual post and core model (101; 112) from the positive working model
(106) of the bore.
2. The method according to any of the preceding claims, wherein the virtual three-dimensional
positive working model (106) is configured to be trimmed, and/or provided with a base,
and/or articulation tested, and/or provided with sectioned preparations preserving
the gingival.
3. The method according to any of the preceding claims, wherein manufacturing comprises
manufacturing the post and core design (110, 111) and/or manufacturing the working
model (106).
4. The method according to any of the preceding claims, further comprising the step of
matching the virtual post and core model (101; 112) with the shape of the dental drill
that created the bore.
5. The method according to any of the preceding claims, further comprising the step of
improving the virtual post and core model (101; 112) and/or the bore model by combining
with shape information of the dental drill that created the bore, shape information
such as a CAD model of the drill.
6. The method according to any of the preceding claims, further comprising the step of
determining the insertion direction (104) of the post and core (21; 41, 42, 43; 51;
110, 111).
7. The method according to any of the preceding claims, wherein a post and core is manufactured
without the post on the basis of the virtual post and core model (101; 102) and wherein
the post and core model (101; 102) comprises a predefined bore for the post.
8. The method according to any of the preceding claims, wherein the post and core is
a split core (41, 42, 43), such as a split core for a multiple root tooth.
9. The method according to claim 8, further comprising virtual filling of one of the
bores when designing the post and core (41, 42, 43) for a case with multiple bores,
and then designing the post for the remaining bore(s).
10. The method according to any of the preceding claims, further comprising the step of
providing and/or using and/or combining with one or more different imaging techniques,
such as X-ray imaging, CT scans, intraoral scans.
11. The method according to any of the preceding claims, for designing and/or manufacturing
at least a part of a dental restoration comprising a post and core (21; 41, 42, 43;
51; 110, 111), said method further comprising any of the steps of:
- providing an interface between the virtual post and core model and the dental restoration
model
- inverting the three dimensional impression model and/or merging the virtual post
and core model with a dental model comprising the prepared tooth, thereby obtaining
a dental model comprising the prepared tooth and the bore,
- adding a base for the dental restoration model,
- determining the insertion direction of the dental restoration,
- removing scan artefacts, and/or
- adding at least one coping or crown to the model.
12. The method according to any of the preceding claims, wherein the crown and/or coping
is designed before designing the post and core (21; 41, 42, 43; 51; 110, 111).
13. The method according to any of the preceding claims, wherein the post and core design(21;
41, 42, 43; 51; 110, 111) automatically is retrieved from an electronic library, so
that the post and core (21; 41, 42, 43; 51; 110, 111) has a correct anatomical fit
relative to the bore.
14. The method according to any of the preceding claims, further comprising the step of
scanning at least a part of an upper jaw dental impression and/or a lower jaw dental
impression, at least one impression comprising an impression of the bore.
1. Computerimplementiertes Verfahren zur Gestaltung und oder Herstellung eines Stiftaufbaus
(21; 41, 42, 43; 51; 110, 111), um einer Bohrung (31) eines Zahns (24) zu entsprechen,
wobei das genannte Verfahren die Schritte umfasst:
a) Erhalten von wenigstens einem Abdruck eines Gebisses, wobei das genannte Gebiss
eine Bohrung umfasst;
b) Scannen des Abdrucks;
c) Bereitstellen einer dreidimensionalen Scan-Darstellung des Abdrucks;
d) Umwandlung der dreidimensionalen Scan-Darstellung in ein virtuelles dreidimensionales
positives Arbeitsmodell (106) des Gebisses und der Bohrung; und
e) Gestalten eines virtuellen Stiftaufbaumodells (101; 112) von dem positiven Arbeitsmodell
(106) der Bohrung.
2. Verfahren nach einem der vorhergehende Ansprüche, wobei das virtuelle dreidimensionale
positive Arbeitsmodell (106) konfiguriert ist, um getrimmt zu werden und/oder mit
einer Basis oder einer getesteten Artikulation bereitgestellt wird und/oder mit abgeteilten
Präparationen, um das Zahnfleisch zu bewahren, bereitgestellt wird.
3. Verfahren nach einem der vorhergehenden Ansprüche, wobei das Herstellen das Herstellen
des Stiftaufbaudesigns (110, 111) und/oder das Herstellen des Arbeitsmodells (106)
umfasst.
4. Verfahren nach einem der vorhergehenden Ansprüche, ferner umfassend den Schritt des
Übereinstimmens des virtuellen Stiftaufbaumodells (101; 112) mit der Forminformation
des Dentalbohrers, der die Bohrung erzeugt hat.
5. Verfahren nach einem der vorhergehenden Ansprüche, ferner umfassend den Schritt der
Verbesserung des virtuellen Stiftaufbaumodells (101; 112) und/oder des Bohrungsmodells
durch Kombination der Forminformation des Dentalbohrers, der die Bohrung erzeugt hat,
mit der Forminformation als ein CAD-Modell der Bohrung.
6. Verfahren nach einem der vorhergehenden Ansprüche, ferner umfassend den Schritt des
Bestimmens der Einführrichtung (104) des Stiftaufbaus (21; 41, 42, 43; 51; 110, 111).
7. Verfahren nach einem der vorhergehenden Ansprüche, wobei ein Stiftaufbau ohne Stift
auf Basis des virtuellen Stiftaufbaumodells (101; 102) hergestellt wird und wobei
das Stiftaufbaumodell (101; 102) eine vordefinierte Bohrung für den Stift umfasst.
8. Verfahren nach einem der vorhergehenden Ansprüche, wobei der Stiftaufbau (41, 42,
43) ein Spaltkern wie ein Spaltkern für einen Zahn mit mehreren Wurzeln ist.
9. Verfahren nach Anspruch 8, ferner umfassend das virtuelle Füllen einer der Bohrungen,
wenn der Stiftaufbau (41, 42, 43) für einen Fall mit mehreren Bohrungen gestaltet
wird und anschließend Gestalten des Stifts für die verbleibende(n) Bohrung(en).
10. Verfahren nach einem der vorhergehenden Ansprüche, ferner umfassend den Schritt der
Bereitstellung und/oder Verwendung und/oder Kombination mit ein oder mehreren verschiedenen
Abbildungstechniken, wie Röntgenstrahlabbildung, CT-Scans, intraorale Scans.
11. Verfahren nach einem der vorhergehenden Ansprüche für die Gestaltung und oder Herstellung
von wenigstens einem Teil einer Dentalrestauration, die einen Stiftaufbau (21; 41,
42, 43; 51; 110, 111) umfasst, wobei das genannte Verfahren ferner irgendeinen der
Schritte umfasst:
- Bereitstellen einer Schnittstelle zwischen dem virtuellen Stiftaufbaumodell und
dem Dentalrestaurationsmodell,
- Invertieren des dreidimensionalen Abbildmodells und/oder Verbinden des virtuellen
Stiftaufbaumodells mit einem Dentalmodell, das den präparierten Zahn umfasst, wodurch
ein Dentalmodell erhalten wird, das den präparierten Zahn und die Bohrung umfasst,
- Zugeben einer Basis für das dentale Restaurationsmodell,
- Bestimmen der Einführungsrichtung der dentalen Restauration,
- Entfernen von Scanartefakten und/oder
- Zugeben von wenigstens einer Stumpfkappe oder Krone zu dem Modell.
12. Verfahren nach einem der vorhergehenden Ansprüche, wobei die Krone und/oder die Stumpfkappe
gestaltet wird, bevor der Stiftaufbau (21; 41, 42, 43; 51; 110, 111) gestaltet wird.
13. Verfahren nach einem der vorhergehenden Ansprüche, wobei das Design des Stiftaufbaus
(21; 41, 42, 43; 51; 110, 111) automatisch von einer elektronischen Bibliothek abgefragt
wird, so dass der Stiftaufbau (21; 41, 42, 43; 51; 110, 111) eine korrekte anatomische
Anpassung relativ zu der Bohrung aufweist.
14. Verfahren nach einem der vorhergehenden Ansprüche, ferner umfassend den Schritt des
Scannens von wenigstens einem Teil eines Dentalabbilds eines Oberkiefers und/oder
Dentalabbilds eines Unterkiefers, von wenigstens einem Abbild, das ein Abbild der
Bohrung umfasst.
1. Procédé implémenté par ordinateur pour concevoir et/ou fabriquer un tenon radiculaire
(21 ; 41, 42, 43 ; 51 ; 110, 111) pour s'adapter à un alésage (31) d'une dent (24),
ledit procédé comprenant les étapes consistant à :
a) obtenir au moins une empreinte d'un jeu de dents, ledit jeu de dents comprenant
un alésage ;
b) balayer l'empreinte ;
c) fournir une représentation de balayage tridimensionnelle de l'empreinte ;
d) transformer la représentation de balayage tridimensionnelle en un modèle de travail
positif tridimensionnel virtuel (106) du jeu de dents et de l'alésage ; et
e) concevoir un modèle de tenon radiculaire virtuel (101 ; 102) à partir du modèle
de travail positif (106) de l'alésage.
2. Procédé selon l'une quelconque des revendications précédentes, dans lequel le modèle
de travail positif tridimensionnel virtuel (106) est configuré pour être fini et/ou
pourvu d'une base et/ou testé en matière d'articulation et/ou pourvu de préparations
sectionnées préservant la gencive.
3. Procédé selon l'une quelconque des revendications précédentes, dans lequel la fabrication
comprend la fabrication du tenon radiculaire (110, 111) et/ou la fabrication du modèle
de travail (106).
4. Procédé selon l'une quelconque des revendications précédentes, comprenant en outre
l'étape d'adaptation du modèle de tenon radiculaire virtuel (101 ; 112) à la forme
de la fraise dentaire qui a créé l'alésage.
5. Procédé selon l'une quelconque des revendications précédentes, comprenant en outre
l'étape d'amélioration du modèle de tenon radiculaire virtuel (101 ; 112) et/ou du
modèle d'alésage en combinant avec les informations de forme de la fraise dentaire
qui a créé l'alésage, des informations de forme telles qu'un modèle CAO de la fraise.
6. Procédé selon l'une quelconque des revendications précédentes, comprenant en outre
l'étape visant à déterminer la direction d'insertion (104) du tenon radiculaire (21
; 41, 42, 43 ; 51 ; 110, 111).
7. Procédé selon l'une quelconque des revendications précédentes, dans lequel un tenon
radiculaire est fabriqué sans le tenon sur la base du modèle de tenon radiculaire
virtuel (101 ; 102) et dans lequel le modèle de tenon radiculaire (101 ; 102) comprend
un alésage prédéfini pour le tenon.
8. Procédé selon l'une quelconque des revendications précédentes, dans lequel le tenon
radiculaire est une chape fendue (41, 42, 43) telle qu'une chape fendue pour une dent
à racines multiples.
9. Procédé selon la revendication 8, comprenant un remplissage virtuel de l'un des alésages
lors de la conception du tenon radiculaire (41, 42, 43) pour un cas à alésages multiples
et, ensuite, la conception du tenon pour le ou les alésages restants.
10. Procédé selon l'une quelconque des revendications précédentes, comprenant en outre
l'étape de mise en oeuvre et/ou d'utilisation et/ou de combinaison avec une ou plusieurs
techniques d'imagerie différentes, telles qu'une imagerie par rayons X, des balayages
CT et des balayages intra-buccaux.
11. Procédé selon l'une quelconque des revendications précédentes, pour concevoir et/ou
fabriquer au moins une partie d'une restauration dentaire comprenant un tenon radiculaire
(21 ; 41, 42, 43 ; 51 ; 110, 111), ledit procédé comprenant en outre l'une quelconque
des étapes consistant à :
- fournir une interface entre le modèle de tenon radiculaire virtuel et le modèle
de restauration dentaire,
- inverser le modèle d'empreinte tridimensionnel et/ou fusionner le modèle de tenon
radiculaire virtuel avec un modèle dentaire comprenant la dent préparée, en obtenant
de la sorte un modèle dentaire comprenant la dent préparée et l'alésage,
- ajouter une base au modèle de restauration dentaire,
- déterminer la direction d'insertion de la restauration dentaire,
- retirer les artéfacts de balayage et/ou
- ajouter au moins un chaperon ou une couronne au modèle.
12. Procédé selon l'une quelconque des revendications précédentes, dans lequel la couronne
et/ou le chaperon est ou sont conçu(e)s avant de concevoir le tenon radiculaire (21
; 41, 42, 43 ; 51 ; 110, 111).
13. Procédé selon l'une quelconque des revendications précédentes, dans lequel le concept
de tenon radiculaire (21 ; 41, 42, 42 ; 51 ; 110, 111) est automatiquement récupéré
auprès d'une bibliothèque électronique de sorte que le tenon radiculaire (21 ; 41,
42, 42 ; 51 ; 110, 111) ait un ajustement anatomique correct par rapport à l'alésage.
14. Procédé selon l'une quelconque des revendications précédentes, comprenant en outre
l'étape de balayage d'au moins une partie d'une empreinte dentaire de mâchoire supérieure
et/ou d'une empreinte dentaire de mâchoire inférieure, au moins une empreinte comprenant
une empreinte de l'alésage.